Predictors of failure to initiate randomized treatment in a large trial of antihypertensive drug therapy in the aged

BACKGROUND: The identification of factors that contribute to noncompliance with trial drug initiation where virtually complete compliance might be expected, may help identify patients whose management is least likely to comply with clinical guidelines and study protocols. METHODS: Examination of cross-sectional and longitudinal data arising from the Second Australian National Blood Pressure Study. Prevalence rate ratios (RR) and 95% confidence intervals (CI) estimated from log-binomial models were used to assess associations between subject characteristics and whether the randomized drug was prescribed at trial randomization. The study population consisted of 6083 hypertensive Australians aged 65 to 84 years. RESULTS: After adjusting for each variable in a multivariate model the following were significant predictors of failure to prescribe RR (95% CI): not previously prescribed antihypertensive drugs 2.89 (2.52-3.32); lower systolic blood pressure (BP) 1.51 (1.59-1.43) or diastolic BP 1.18 (1.22-1.13); younger age 80 to 84 v 65 to 79 years 0.75 (0.59-0.95); total cholesterol >or=6.6 v